Yeah I know DA do the 65.21.61.62-da.direct thing which is really handy.
Name me 1 reason why. Because I can name you a couple of reasons why it's not. Starting with teaching people the wrong way, lot don't even know how to set up a hostname correctly and then come complaint that they have mail issues, which we almost had not in the early days.
Otherwise I wouldn't have needed to write that hostname manual I did, which lots of people used (or rather had to use) to fix things.
Second is that yes you can visit the panel, but it's anyway best to not do anything until the background things are installed, otherwise the changes are not integrated into for example apache and you get odd things like missing domain names or other errors.
So if you have to wait anyway, you can just as well setup things correctly and learn to do it correctly and then an LE SSL certificate is there fast enough with the autoSSL.
DS does not need to be an exception. Just use a subdomain of your domain as hostname is very well possible like ds.domain.com or something like that. We have it that way and even with SSL!
Seems LE is the first one doing it, and I'm sure there is a reason others didn't do it before. I can't imagine an organisation not wanting to have to setup their network correctly with domain name, certainly not these days.
Shortlived yes, well... 3 months. And people asked this. Yes well people always ask for things, doesn't always mean those things are good or wise.
So until now I don't see any benefits at all, except for a few hobbyists and website devs. Ofcourse I could be wrong, maybe some have some great examples.
But you don't need to convince me. I just gave my opinion. Lets talk in a few years and see if my thoughts were wrong or right. But I fear the most and probably it's even not conform RFC.